In Germany, sewage sludge is currently disposed in agriculture and landscaping or by thermal treatment. Due to the increasing public and political focus on soil, plant and environmental protection, the direct supply of sewage sludge to agriculture is increasingly viewed critically. This is due to the risk of a possible release of contained (organic) pollutants into the environment (food, groundwater). Therefore, the utilisation of sewage sludge in agriculture will be restricted by law in Germany in the future.
However, sewage sludge also contains important nutrients, such as phosphorus in particular, which has been classified as a critical raw material by the EU Commission since 2014. As a result, EU countries are obliged to take action to increase use efficiency and recycling. From 2029, thermal treatment will step by step become obligatory for wastewater treatment plants and, in case of a phosphorus content greater than 2 % in the dry matter, there is also a requirement to carry out phosphorus recycling either before or after thermal treatment. A large number of recycling processes are currently still in development and it is unclear whether these technologies will be technically mature and available with sufficient treatment capacity at the required time.
In the project, research and stakeholder interviews will be used as a basis for analysing the available thermal treatment and phosphorus recycling capacities and forecasting further capacity requirements until 2029. Furthermore, the state of the art of thermal sewage sludge treatment technology for alternative thermal treatment processes and phosphorus recycling technology is determined. The processes identified will be evaluated comparatively in terms of efficiency and technology readiness level, for example. The aim is to provide valuable knowledge for the further development of a German phosphorus strategy.
The project is carried out in cooperation with the ISA institute at RWTH Aachen University on behalf of the German Federal Environment Agency (UBA) and is financed with federal funds.